Colantotte Authentic X1 Knee Supporter Magnet Designed in Japan [Japan Import] Authentic Colantotte Products Designed in Japan QTR: ONE piece . NOT A PAIR. Spec: 100mT(1000G) Ferrite Permanent Magnet x 4 Please check the size before purchasing. For sizing, measure the upper-knee circumference. S: approx. 13.9 - 14.6in (33-37cm) M: approx. 13.8 -15.4 in (35-39cm) L: approx. i14.6 - 16.1in (37-41cm) XL: approx. 15.4 - 17.0in (39-43cm) The package is subject to change.